A primary purpose of this Laboratory is to test the hypothesis that the striatal complex plays a basic role in organizing the expression of species-typical behavior. Anatomical and histochemical findings suggest that some of the large neurons of the interior zone of olfactory tubercle (ventral striatum) may be a rostroventral extension of the globus pallidus. Accordingly, in rats the large cells of the tubercle are being compared with those of the globus pallidus with respect to their content of gluctamic acid decarboxylase (GAD) (the synthesizing enzyme for gamma amino butyric acid (GABA)) and of ferritin. Both ferritin and GAD can be localized by immunochemical methods. Comparative observations are also to be made on lizards.